Multi-layer coated porous materials and methods of making the same

ABSTRACT

Multi-layer coated materials and methods of making them are disclosed. In a specific embodiment, a porous polymeric substrate is pre-activated and immersed in a polyelectrolyte solution to form a first layer having an electric charge and at least one functional group. The coated material is next immersed in a second solution of a material having an electric charge opposite of that of the first layer to provide a bi-layer coating. This process can be repeated to form multi-layer coatings on porous substrates.

1. RELATED APPLICATIONS

This application claims priority to U.S. provisional patent applicationNos. 60/315,043 and 60/315,044, both filed on Aug. 28, 2001, thecontents of which are incorporated by reference herein.

2. FIELD OF THE INVENTION

This application is directed, in part, to multi-layer coated substrates,preferably porous polymeric substrates, wherein the coating is made upof at least two layers, and to methods of making the same.

3. BACKGROUND OF THE INVENTION

Porous materials, including metal, ceramic, glass and polymericmaterials, have increasingly been used in a variety of applications,such as filtration, aeration, wicking, and implant and other biomedicaldevices. For example, porous polymeric materials can be used in medicaldevices that serve as substitute blood vessels, synthetic andintra-ocular lenses, electrodes, catheters, and extra-corporeal devicessuch as those that are connected to the body to assist in surgery ordialysis. Porous polymeric materials can also be used as filters for theseparation of blood into component blood cells and plasma, microfiltersfor removal of microorganisms from blood, and coatings for ophthalmiclenses to prevent endothelial damage upon implantation. Porous materialshave also been used in diagnostic devices such as lateral flow devices,flow through devices and other immunoassay devices.

It is often necessary to alter the surface properties of a porousmaterial, since the application of porous materials is often limited bytheir lack of chemical functional group and/or their hydrophobicproperties, which may be disadvantageous in applications such as liquidfiltration, extraction, separation and immobilization of smallmolecules, polymers or large biomolecules. For example, proteins willoften denature when placed in contact with hydrophobic materials, andhydrophobic porous materials cannot wick aqueous solutions. Contactlenses, implants, and related devices that are in intimate contact withthe body must have hydrophilic surfaces that are biologicallycompatible.

Attempts have been made to modify porous materials, but with mixedsuccess. For example, U.S. Pat. No. 4,250,029 discloses a method ofmanufacturing ionic rejection membrane by coating differently chargedpolyelectrolytes onto a membrane with a neutral polymer layer betweentwo electrolytes. The patent, however, is directed to thin ion rejectionmembranes only.

U.S. Pat. No. 4,619,897 discloses that the physical and/or chemicalproperties of a plastic surface can be changed by adhering or bonding adifferent material to it.

U.S. Pat. No. 4,845,132 discloses a method that uses plasma andhydrophilic monomer to produce a hydrophilic porous membrane. However,the resulted polymer film deposited by this method is not stable; andhydrophilic monomer or polymers tend to leach out.

U.S. Pat. No. 5,540,837 discloses a method of producing permanenthydrophilic fluoropolymers by coating a charged polyelectrolyte complexon top of the fluoropolymer. The application of this patent, however, islimited to the fluorinated polymer membrane and the adhesion between thepolyelectrolyte complex and fluorinated polymer substrate is poor due tothe lack of strong interactions between the polyelectrolyte complex andthe fluorinated membrane.

U.S. Pat. No. 5,695,640 discloses a method for producing a hydrophilicporous article by treating a porous article with the mixture ofpolyamide and calcium chloride methanol solution. However, the stabilityof the hydrophilicity obtained by this method is poor.

U.S. Pat. Nos. 5,700,559; 5,807,636 and 5,837,377 disclose a method ofmodifying the surfaces of plastics with plasma and sequential PEIsolution treatment to provide the plastics with hydrophilicity. Thismethod can allegedly provide relatively stable hydrophilic plastics.However, the wicking rate of the plastics deteriorates during thestorage.

U.S. Pat. No. 5,856,246 discloses a method of surface modification ofmaterials using water soluble polycation and long chain surfactant oralkyl-substituted polyanion to make fiber, textiles, polymer andmembrane permanent hydrophobic or oleophobic. The method disclosedtherein, however, is suitable only for charged materials, not forneutral polymers such as polyolefins.

U.S. Pat. Nos. 5,914,182 and 5,916,585 disclose a method for improvingporous membrane's biomaterial binding properties by treating the porousmembrane with a polymer surfactant solution. The polymeric surfactantbinds to the support material through hydrophobic interactions. Thefirst layer is then crosslinked by a chemical reagent. A secondaryhydrophilic layer is brought to the membrane by dipping the membraneinto a hydrophilic polymer solution. This hydrophilic polymer coatingallegedly can improve biomolecule binding and form covalent bonds withthe first layer. This method, however, only works on ultrathinmembranes. Further, the binding between the polymer surfactant and themembrane support is weak because the binding force is based onhydrophobic interaction. In addition, the crosslinking reagentglutaldehyde used therein is highly toxic.

U.S. Pat. No. 6,020,175 discloses a method of producing multiple layeredfunctional thin films (such as protein and dye) onto solid supports byimmersing charged solid substrates into an admixed polymerion-functional molecule solution having a net opposite electric charge.This step can be repeated to form multi-layered film. The patent isdirected to solid non-porous materials.

U.S. Pat. No. 6,060,410 discloses a method of coating a hydrophobicpolymer substrate with a nonstoichiometric polyclectrolyte complex insolution.

Thus, there is still a need for materials, especially porous materials,with controllable and stable wicking rates, low leaching rates, and/orfunctional groups that enhance the materials' application potential infiltration, separation, diagnostics and medical device areas. Morespecifically, there is a need to provide porous polymeric materials withcontrollable wicking rates, biomolecular binding abilities, chemicalreactivities, and ionic selection abilities.

4. SUMMARY OF THE INVENTION

The present invention provides multi-layer coated materials and methodsof making such materials. Specific methods utilize solution treatmentwith sequential polyelectrolyte solution.

The materials of this invention can be used in a variety of applicationsas filters, films, lateral flow membranes, conjugate pads, extractionmaterials, and blood separation materials. Materials of this inventioncan be produced economically and/or consistently and can exhibit one ormore of the following properties: permanent hydrophilicity orhydrophobicity; high density functional groups; limited leaching; strongand/or specific binding ability to a variety of reagents such asproteins and other biomolecules; controllable and/or narrowerdistribution of porosities; controllable and wide wicking rates;flexible strength for different applications.

In one aspect, the present invention provides a multi-layer coatedmaterial comprising a substrate, a first layer, and a second layer. Thesubstrate comprises a sintered porous polymeric material; the firstlayer comprises molecules bound to a surface of the substrate throughcovalent bonds, electrostatic interactions, or combinations thereof; andthe second layer comprises molecules bound to the first layer throughcovalent bonds, electrostatic interactions, or combinations thereof.

In a specific embodiment, the polymeric material is a polyolefin,polyester, polyurethane, polycarbonate, polyetheretherketone,poly(phenylene oxide), poly(ether sulfone), or nylon. In anotherspecific embodiment, the polyolefin is ethylene vinyl acetate, ethylenemethyl acrylate, polyethylene, polypropylene, ethylene-propylene rubber,ethylene-propylene-diene rubbers, poly(1-butene), polystyrene,poly(2-butene), poly(1-pentene), poly(2-pentene),poly(3-methyl-1-pentene), poly(4-methyl-1-pentene),1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene; polyisoprene,polychloroprene, poly(vinyl acetate), poly(vinylidene chloride),poly(vinylidene fluoride), poly(tetra fluoro ethylene), or mixturethereof.

In one embodiment, the molecules of the first layer and the second layerof the multi-layer coated material are independently selected frompolyelectrolyte, surfactant, neutral polymer, small molecule,biomolecule, or combination thereof.

Specific polyelectrolytes include, but are not limited to, phosphates,polyethyleneimides, poly(vinylimidazoline), quaterized polyacrylamides,polyvinylpyridines, poly(vinylpyrrolidone), polyvinylamines,polyallylamines, chitosans, polylysines, poly(acrylate trialkyl ammoniasalt ester), cellulose, poly(acrylic acid), polymethylacrylic acid,poly(styrenesulfuric acid), poly(vinylsulfonic acid), poly(toluenesulfuric acid), poly(methyl vinyl ether-alt-maleic acid), poly(glutamicacid), surfactants, dextran sulfates, hyaluronic acid, heparin, alginicacid, adipic acid, chemical dyes, proteins, enzymes, nucleic acids,peptides, and a salts, esters, and copolymers thereof.

Specific neutral polymers include, but are not limited to, isocyannatedterminated polymer, epoxy-terminated polymer, or hydroxylsuccinimideterminated polymer. More specific examples of neutral polymer includepolyurethane, poly(ethylene glycol), and polysiloxane.

Specific mall molecules include, but are not limited to, sodiumdodecylsulfonate, dodecyltrimethylamonium bromide, phosphate, sulfonate,bronate, dye, lipid, metal ion, or surfactant containing fluorine.

Specific biomolecules include, but are not limited to, proteins,enzymes, lipids, hormones, peptidse, nucleic acids, oligonucleic acids,DNA, RNA, sugars, or polysaccharides.

In another specific embodiment of the multi-layer coated material ofthis invention, the first layer comprises molecules of polyethylenimineand the second layer comprises molecules of a poly(acrylic acid), acopolymer containing poly(acrylic acid), or a surfactant, such as afluorinated surfactant. Alternatively, the first layer comprisesmolecules of polyallylammoniumchloride, and the second layer comprisesmolecules of polyvinylsulfate.

In another embodiment, the substrate is further coated with one or moreadditional layers bound to the second or one of the additional layersthrough covalent bonds, electrostatic interactions, or combinationsthereof. For example, the substrate can be coated with three layers withthe first layer comprising molecules of polyethylenimine, the secondlayer comprising molecules of a polyallylamine, and the third layercomprising of molecules of polyethylenimine, polyvinylamine, or asurfactant.

Another aspect of this invention provides a method of producing amulti-layer coated material. The method comprises coating a first layerof molecules onto a surface of a substrate through covalent bonds,electrostatic interactions, or combinations thereof; and coating asecond layer of molecules onto said first layer through covalent bonds,electrostatic interactions, or combinations thereof.

In a specific embodiment, the method further comprises surfaceactivating the substrate, using means such as, but not limited to,chemical treatment, plasma discharge, corona discharge, electron-beam,and combinations thereof.

Specific materials that can be used as the substrate for the methodinclude, but are not limited to, metals, alloys, ceramic materials,glasses, carbon, silicon, and polymers. The substrate may be solid orporous. A specific substrate material is a sintered porous polymer.

Specific polymers that can be used as the substrate for the methodinclude, but are not limited to, polyolefin, polyester, polyurethane,polycarbonate, polyetheretherketone, poly(phenylene oxide), poly(ethersulfone), and nylon. Specific examples of polyolefin include, but arenot limited to, ethylene vinyl acetate, ethylene methyl acrylate,polyethylene, polypropylene, ethylene-propylene rubber,ethylene-propylene-diene rubbers, poly(l-butene), polystyrene,poly(2-butene), poly(1-pentene), poly(2-pentene),poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), 1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene; polyisoprene,polychloroprene, poly(vinyl acetate), poly(vinylidene chloride),poly(vinylidene fluoride), poly(tetra fluoro ethylene), and mixturesthereof.

In another specific embodiment of the method, the molecules of the firstlayer and the second layer are independently polyelectrolytes,surfactants, neutral polymers, small molecules, biomolecules, andcombinations thereof. In another embodiment, the method furthercomprising coating one or more additional layers of molecules onto thesecond or the additional layer through covalent bonds, electrostaticinteractions, or combinations thereof.

5. BRIEF DESCRIPTION OF THE DRAWINGS

To better understand specific novel aspects of the invention, referencecan be made to the figures described below:

FIG. 1 provides a general schematic of various embodiments of theinvention having a two-layer coating, wherein molecules that make up acoating are indicated by circles, circles without a plus or a minusindicate a neutral molecule, circles with a “+” indicate a cationicmolecule or a molecule containing a cationic moiety, and circles with a“−” indicate a anionic molecule or a molecule containing an anionicmoiety;

FIG. 2 illustrates the Wicking rates for porous materials treated withdifferent polyelectrolytes;

FIG. 3 illustrates the leaching amounts for differently washed PEI/PAAtreated porous materials;

FIG. 4 illustrates the leaching amounts for PEI/PAA treated porousmaterial in PBS and pure water;

FIG. 5 illustrates IgG binding amounts at different pH for differentlytreated porous materials (at 0.01 M PBS);

FIG. 6 illustrates IgG binding amount at different ionic strength fordifferently treated porous materials;

FIG. 7 illustrates IgG binding amounts on various PEI/PAA treated porousmaterials; and

FIG. 8 illustrates IgG binding amounts on porous materials treated withdifferent polyelectrolytes.

6. DETAILED DESCRIPTION

This invention is directed, in part, to materials having multilayercoatings, and in particular to porous materials having multilayercoatings. The invention is further directed to methods of making suchmaterials and to methods of modifying the surface properties of porousand solid materials. Specific materials of the invention are durable,have controlled wicking properties, and unique physical and chemicalsurface properties.

Materials of this invention can be used as filters, films, lateral flowmembranes, conjugate pads, extraction materials, and blood separationmaterials. Therefore, the applications of the present invention'smaterials include, but are not limited to, filtration and extractiondevices, chromatographic devices such as thin-layer chromatographicdevices, lateral flow devices, flow through devices, fast screeningdevices, combinatory chemistry matrix, microfluidic devices, and cellculture materials.

Specific materials of this invention can be produced economically and/orconsistently and can exhibit one or more of the following properties:permanent hydrophilicity or hydrophobicity; high density functionalgroups; limited leaching; strong and/or specific binding ability to avariety of reagents such as proteins and other biomolecules;controllable and/or narrower distribution of porosities; controllableand wide wicking rates; flexible strength for different applications.

Materials of the invention can be made into sheets or membranes ofvarious thicknesses and shapes. In a specific embodiment, the thicknessof the material ranges from about 1 μm to about 10 mm. In anotherembodiment, the thickness ranges from about 1 μm to about 1 mm. Morespecifically, the thickness ranges from about 10 μm to about 500 μm. Thematerials of the invention can also be made into various shapesaccording to the specific device and assay desired.

In another specific embodiment, the material of this invention has a lowsurface tension, e.g., below about 50 dynes/cm, more typically belowabout 40 dynes/cm. In other specific embodiments, the material compriseswetting agents or is surface activated and then coated with one or morelayers of a polyelectrolyte, a surfactant, a neutral polymer, a smallmolecule, a biomolecule, or a combination thereof. Functional groups areattached to a surface of particular materials of the invention that canbe used to covalently and/or electrostatically bind other molecules(e.g., target molecules) onto the surface. Examples of target moleculesinclude, but are not limited to, enzymes, proteins, cells, nucleicacids, peptides, ligands, DNA and RNA.

The material encompassed by one embodiment of the invention isillustrated in FIG. 1. This material comprises a porous substrate withat least one surface being coated with a multi-layer coating. Each layerof the multilayer coating can be neutral (e.g., as shown in FIG. 1A) orcan contain localized and/or net cationic or anionic charges (e.g., asshown in FIGS. 1B, 1C, 1D, 1E, and 1F). The layers can be adhered to thesubstrate surface and to each other by covalent and/or electrostaticinteractions. For example, molecules forming the layer in direct contactwith the substrate (first layer) can be covalently bound to its surface,and molecules forming the second surface (second layer) can be adheredto the first surface by electrostatic interactions (e.g., as shown inFIG. 1B). Other scenarios include first layer electrostaticinteractions/second layer covalent bonds; first layer covalentbond/second layer covalent bond; first layer electrostaticinteractions/second layer electrostatic interactions; and mixed covalentbonds and electrostatic interactions for both first and second layers.Because the molecules forming each layer can bond to the material belowit by multiple covalent and/or electrostatic interactions, typicalmaterials of the invention have highly stable coatings that areresistant to delamination and/or dissociation.

6.1 Materials

Materials of the invention, which comprise a substrate and a multilayercoating, can be made using methods described herein from materials suchas, but not limited to, those discussed below.

6.1.1. Substrates

Substrates that can be used to provide materials of the invention can besolid or porous, and can come in any of a variety of shapes and forms.For example, substrates can be blocks, films, molded parts, tubes,fibers, and sheets. Preferred porous substrates have an average poresize of from about 0.001 μm to about 1000 μm, more preferably from about0.01 μm to about 500 μm, and most preferably from about 0.1 μm to about200 μm.

Solid and porous substrates can be made of a variety of materials, suchas, but not limited to: metals (e.g., Cu, Ag, Au, Al, Zn, and Fe);alloys; glasses; ceramics; carbon black; silica; silicon; and polymericmaterials or plastics. As used herein, “porous materials” or “poroussubstrate” refers to a material or a substrate that has a surface withone or more pores or a surface that is uneven, undulating, or not smoothor flat, such as a woven, non-woven, compressed, perforated, or etchedmaterial or substrate.

A specific substrate of the present invention is a sintered porouspolymeric or plastic material. Porous polymeric materials can usually bemade from a variety of thermoplastic and thermoset materials usingmethods known in the art such as, but not limited to, sintering andcasting. According to the present invention, the porous polymericmaterials are made through a sintering process, as discussed herein.Thus, suitable polymers for the substrate are those that can be sinteredto form sheet or membrane-like porous materials. Examples of suitablethermoplastic or thermoset materials include, but are not limited to,polyolefins, nylons, polycarbonates, nitrocellulose, fiberglass, andpoly(ether sulfones).

Examples of polyolefins suitable for the present invention include, butare not limited to, ethylene vinyl acetate (EVA); ethylene methylacrylate (EMA); polyethylenes such as, but not limited to, low densitypolyethylene (LDPE), linear low density polyethylene (LLDPE), highdensity polyethylene (HDPE), and ultra-high molecular weightpolyethylene (UHMWPE); polypropylenes; ethylene-propylene rubbers;ethylene-propylene-diene rubbers; polystyrene; poly(1-butene);poly(2-butene); poly(1-pentene); poly(2-pentene);poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;polychloroprene; poly(vinyl acetate); poly(vinylidene chloride);poly(vinylidene fluoride); poly(tetra fluoro ethylene); and mixtures andderivatives thereof.

Specific EVA materials include, but are not limited to, those in theMicrothene MU® and Microthene FE® series manufactured by Equistar,Houston, Tex., such as Microthene MU 763-00 (9% vinyl acetate) andMicrothene FE 532-00 (9% vinyl acetate). Specific EMA materials include,but are not limited to, those in the Optema TC® series manufactured byExxon Chemical Company, Baton Rouge, La., such as Optema TC-110 (21.5%methyl acrylate). Specific polyethylene materials include, but are notlimited to, those in the Exact® series manufactured by Exxon ChemicalCompany, such as Exact SLX-9090, Exact 3024, Exact, 3030, Exact 3033,Exact 4011, Exact 4041, Exact SLP-9053, Exact SLP-9072, and ExactSLP-9095. Specific examples of LDPE include, but are not limited to,those in the 20 series manufactured by DuPont Chemical Company,Wilmington, Del., such as 20 series 20, 20 series 20-6064, 20 series2005, 20 series 2010, and 20 series 2020T. Specific examples of LLDPEinclude, but are not limited to, those in the Exact® series manufacturedby Exxon Chemical Company, such as Exact 3022 and Exact 4006. Specificexamples of HDPE include, but are not limited to, those in the EscoreneHX® series manufactured by Exxon Chemical Company, such as EscoreneHX-0358.

Ultra-high molecular weight polyethylenes include, but are not limitedto, UHMWPE having a molecular weight greater than about 1,000,000.Typically, UHMWPE displays no measurable flow rate under normal testprocedures. See, U.S. Pat. No. 3,954,927. Ultra-high molecular weightpolyethylene also tends to have enhanced mechanical properties comparedto other polyethylenes, including, but not limited to, abrasionresistance, impact resistance and toughness. Polyethylenes having weightaverage molecular weights of 1,000,000 or higher, which are includedwithin the class designated as UHMWPE, typically an intrinsic viscosityin the range of about 8 or more. Specific examples of UHMWPE include,but are not limited to, Hostalen GUR® sold by Ticona Inc., League City,Tex.

Polypropylenes include, but are not limited to, the Polyfort® seriesmanufactured by A Shulman Co., Akron, Ohio, such as FPP 2320E, 2321E,2322E, 2345E, PP2130, and PP2258; the Acctuf® series manufactured by BPAmoco Corporation, Atlanta, Ga., such as Acctuf 3045, Amoco 6014, andAmoco 6015; the Aristech® series manufactured by Aristech ChemicalCorp., Pittsburgh, Pa., such as D-007-2, LP-230-S, and TI-4007-A; theBorealis® series manufactured by BASF Thermoplastic Materials, SaintPaul, Minn., such as BA101E, BA110E, BA122B, BA204E, BA202E, and BA124B;the Polypro® series manufactured by Chisso America Inc., Schaumburg,Ill., such as F1177 and F3020; the Noblen® series manufactured byMitsubishi Petrochemical Co. Ltd., Tokyo, Japan, such as MA8; theAstryn® series manufactured by Montell USA Inc., Wilmington, Del., suchas 68F4-4 and PD451; the Moplen® series manufactured by Montell USAInc., such as D 50S, D 60P, and D 78PJ; and the Pro-Fax® seriesmanufactured by Montell USA Inc., such as 6723, 6823, and 6824.

A specific substrate material of this invention is sintered porouspolymeric material, which can be surface activated and/or coated withone or more layers of a variety of materials. Depending on itsmanufacturing process, a porous polymeric material can thus containregular arrangements of channels and pores of random and/or well-defineddiameters and/or varying shapes and sizes.

As a practical matter, the term “pore” is an artificial one that canhave various meanings. According to the present invention, the averagesizes, shapes, and number of pores in a material can be determined bytaking a cross-section of the material. For the purpose of thisinvention, holes and depressions in the cross-section are consideredpores. And, while only two-dimensional sizes and shapes of those porescan be determined from the cross-section, information about their thirddimension (e.g., their depth) can be determined from a secondcross-section, orthogonal to the first. Also, average pore size, porevolume, and/or surface area can be inferred from measurements obtainedusing a mercury intrusion porisometer. For the purpose of thisinvention, pore sizes are typically referred to in terms of theiraverage diameters, even though the pores themselves are not necessarilyspherical.

The particular method used to form the pores or channels of a porouspolymeric material and the resulting porosity (i.e., average pore sizeand pore density) of the porous material can vary according to thedesired application for which the final membrane be used. The desiredporosity of the matrix can also be affected by the polymeric materialitself, as porosity can affect in different ways the physical properties(e.g., tensile strength and durability) of different materials.

A specific porous polymeric material of this invention has an averagepore size of from about 0.1 μm to about 200 μm, more specifically fromabout 1 μm to about 50 μm, and from about 1 μm to about 20 μm. Forpurpose of this invention, pore size and pore density can be determinedusing, for example, a mercury porisometer, scanning electron microscopy,or atomic force microscopy.

Although the porous polymeric material of the present invention can bemade from the materials discussed above, many other materials that arecommercially available can also be used for the purposes. Suitablesubstrates can be purchased from Porex Technologies, Fairburn, Ga.

6.1.2. Coatings

The multilayer coatings of the present invention comprise at least twolayers, the first of which is adhered (e.g., covalently and/orelectrostatically) to the surface of the substrate, and the second ofwhich is adhered (e.g., covalently and/or electrostatically) to thefirst layer. Using methods and materials disclosed herein as well asones known to those of skill in the art, additional layers can beadhered atop the second layer and to one another (e.g., covalentlyand/or electrostatically).

The substrate of the present invention can be coated with one or morelayers of coating to make a material suitable for use in a wide varietyof applications, such as analyte detection. In a specific embodiment, asintered porous plastic substrate is surface activated, as discussedherein, before being coated.

Examples of the materials that can be used as the first layer, secondlayer, or further additional layers include, but are not limited to,charged polymers or polyelectrolytes, surfactants, neutral polymers,small molecules, biomolecules, and combinations thereof. Some of thecharged polymers contain a net cationic or anionic charge, or localizedcationic or anionic charges (e.g., zwitterions), or can provide net orlocalized charges when adhered or deposited onto the substrate and/orlayer(s) coating the substrate. For example, layers can be formed fromorganic or inorganic salts.

Organic materials that can be used to form coatings of the inventioninclude, but are not limited to, organic polymers, monomers, andbiomolecules. Preferred organic materials contain net and/or localizedcationic or anionic charges. Organic materials that are preferred fordirect adhesion to the surface of a substrate are polymers, such as, butnot limited to, single and copolymers (e.g., random, graft, and blockcopolymers). Polymers used in coating in the present invention have amolecular weight of from about 1,00 to about 5 million, preferably, fromabout 10,000 to about 2 million.

Specific examples materials from which first, second, and additionallayers can be formed are materials that contain a net cationic oranionic charge, or localized cationic or anionic charges (e.g.,zwitterions), or can provide net or localized charges when adhered ordeposited onto the substrate and/or layer(s) coating the substrate. Forexample, layers can be formed from organic or inorganic salts.

Materials that can be used for direct adhesion to the surface of asubstrate include polymers, such as, but not limited to, single andcopolymers (e.g., random, graft, and block copolymers). Polymers used incoating in the present invention have a molecular weight of from about1,00 to about 5 million, preferably, from about 10,000 to about 2million.

In a specific embodiment of the present invention, materials for thefirst layer and second layer include, independently, one or more of asurfactant, phosphate, polyethyleneimide (PEI), poly(vinylimidazoline),quaterized polyacrylamide, polyvinylpyridine, poly(vinylpyrrolidone),polyvinylamines, polyallylamines, chitosan, polylysine, poly(acrylatetrialkyl ammonia salt ester), cellulose, poly(acrylic acid) (PAA),polymethylacrylic acid, poly(styrenesulfuric acid), poly(vinylsulfonicacid), poly(toluene sulfuric acid), poly(methyl vinyl ether-alt-maleicacid), poly(glutamic acid), dextran sulfate, hyaluronic acid, heparin,alginic acid, adipic acid, chemical dye, protein, enzyme, nucleic acid,peptide, or a salt or ester thereof. More specifically, materials forthe first layer include a polyethyleneimide, poly(vinylpyrrolidone), orcombinations thereof.

Examples of polymers or copolymers that contain cationic charges includethose that contain quaternary groups of nitrogen and phosphor, polymersthat contain primary and secondary amine groups. These polymers can becharged in certain range of pH in solutions. Particular examplesinclude, but are not limited to, surfactants, polyethylenimine (PEI),poly(vinylimidazoline), quaternized polyacrylamide, polyvinylpyridine,poly(vinylpyrrolidone), polyvinylamines, polyallylamines, chitosan,polylysine, poly(acrylate trialkyl ammonia salt ester), cellulose, andsalts thereof.

Examples of polymers or copolymers that contain anionic charges include,but are not limited to, poly(acrylic acid) (PAA) and its sodium salt,polymethylacrylic acid and its sodium salt, poly(styrenesulfuric acid)(PSSA) and its sodium salt, celluloses that contain sulfonated orcarboxylic acid groups, poly(vinylsulfonic acid), poly(toluene sulfuricacid), poly(methyl vinyl ether-alt-maleic acid) and ester, poly(glutamicacid), dextran sulfate, hyaluronic acid, heparin, alginic acid, adipicacid, sodium carboxymethyl cellulose (CMC), anionic charged polymersurfactants, and molecules containing a phosphate group.

Polymers and copolymers that contain both cationic and anionic moietiescan also be used to provide materials of this invention. For example,about one to about 99 percent of the repeat units of a polymer cancontain cationic moieties, preferably from about 20 to 80 percent.Amphoteric polymers (i.e., polymers wherein about 50 percent of therepeat units contain cationic groups and about 50 percent containanionic groups) can also be used. Polymers and copolymers may havevarying charge densities (i.e., the ratio of charge to the number ofrepeat units). For example, polymers with charge densities of from aboutone to 100 percent, preferably from about 20 to about 100 percent, canbe used.

Neutral polymers can also be used to form the multilayer coatings of theinvention, particularly polymers capable of forming covalent bonds withthe components of other layers or with the substrate surface underconditions such as those discussed herein. Examples of such neutralpolymers include, but are not limited to: isocyannated terminatedpolymers, including polyurethane, and poly(ethylene glycol) (PEG);epoxy-terminated polymers, including PEG and polysiloxanes; andhydroxylsuccinimide terminated polymers.

Small molecules can also be used to provide layers and coatings of theinvention. Specific small molecules encompassed by the present inventionhave a molecular weight of from about 10 to about 10,000. Morespecifically, the molecular weight of the small molecules ranges fromabout 50 to about 2,000 and from about 50 to about 1,000. Preferredsmall molecules are charged. Examples of small molecules include, butare not limited to, s surfactant, such as zonyl surfactant (DuPont),SURFYNOL(Air product), FLUORAD (3M), sodium dodecylsulfonate (SDS),dodecyltrimethylamonium bromide (DTAB), phosphates, sulfonates,bronates, dyes, lipids, and metal ions. Small molecules also includeother specific surfactants such as cationic surfactants, anionicsurfactants, amphoteric surfactants, and fluorine containingsurfactants.

Coatings of the invention can also be made from biomolecules. Preferredbiomolecules contain net or localized charges. Examples of biomoleculesinclude, but are not limited to, proteins, enzymes, lipids, hormones,peptides, nucleic acids, oligonucleic acids, DNA, RNA, sugars, andpolysaccharides. Examples of proteins include, but are not limited to,immunoglobulins G (IgGs) and albumins, such as bovine serum albumin(BSA) and human serum albumin.

6.2. Process of Making the Materials

Materials of the invention can be readily prepared using methodsdescribed herein. In a specific method, the surface of a substrate isactivated using chemical treatment, plasma, electron-beam (e-beam),and/or corona discharge methods known in the art. This activation altersthe surface by cleaving chemical bonds to allow the formation ofhydrophilic and/or chemically active moieties such as, but not limitedto, hydroxy, amine, and carboxylic groups. Of course, the particulargroups formed will depend on the chemical composition of the substratesurface and the methods and conditions used to activate it. Often, theactivation of a hydrophobic plastic surface will provide a hydrophilic,electrically charged surface.

Of the various methods that can be used to activate a substrate surface,plasma treatment and corona discharge are preferred for the activationof plastics, and porous plastics in particular. Plasmas that can be usedto provide negatively charged porous plastic surfaces include, but arenot limited to, plasmas of argon, oxygen, nitrogen, methanol, ethyleneoxide, and acetone. Plasmas that can be used to provide positivelycharged surfaces include, but are not limited to, ammonia andethylenediamine. Depending on the composition of the substrate, it size,and the particular plasma used, the time necessary to achieve a desiredsurface will vary. Typical times can vary from about 1 minute to aboutan hour. Similarly, the power necessary to achieve the desired plasmawill typically vary from about 50 W to about 1000 W.

6.2. 1. Sintering

A specific embodiment of this invention uses porous plastic substratesmade through sintering. Many suitable sintering process of making aporous polymer can be used to form the sintered porous polymericmaterial of the present invention. Sintering is a process that fusesdiscrete particles, such as polymer particles, together by heat. Forexample, polymer particles can be first packed in a mold or othercontainers or substrates. The particles are then heated to a temperaturethat usually melts only the outer surface or shell of the particles. Theparticles are then fused together at this temperature and cooled down toa lower temperature, such as room temperature, to form the sinteredproduct.

In a specific embodiment, the polymeric particles are made usingunderwater pelleting, e.g., as disclosed in U.S. patent application Ser.No. 09/447,654 of Yao et al., filed Nov. 23, 1999, the content of whichis incorporated herein by reference.

According to one embodiment the present invention, a mixture is firstformed that comprises the polymeric material (e.g., particles ofpolymers as discussed in Section 6.1) and other optional materials(e.g., wetting agents and surfactants). The materials are preferably inpowder form, and are mixed to ensure an even distribution of eachthroughout the mixture. The mixture is then heated to the sinteringtemperature of the material, optionally under pressure, to provide asintered porous polymeric material.

Those skilled in the art will recognize that the average pore size ofthe porous polymeric material will depend, at least in part, on theaverage particle size of the polymeric material, the sinteringtemperature, and the pressure—if any—applied to the mixture duringsintering. If the particles of the other optional materials, if any, aresmaller than the average pore size of the porous material, they will betrapped within pores of the material during the sintering process, andmay be adhered to the walls of those pores. If particles of the otheroptional materials, if any, are larger than the average pore size of theporous material, they will be incorporated within the porous material asinclusions.

Sintering can occur on a solid support or within a mold to yield a finalproduct that can be cut into pieces of desired shape. The use of moldsis preferred where the desired shape of the self-sealing medium iscomplex.

6.2.2. Surface Activation

In order to coat a surface of some substrates, it is preferred that thesurface be activated before the coating is applied.

The surface of a substrate can be activated using one or more methodsknown in the art such as, but not limited to, chemical treatment, plasmadischarge, electron-beam (e-beam) discharge, and corona discharge. Thisactivation alters the surface of the substrate, by means such ascleaving chemical bonds, to allow the formation of hydrophilic and/orchemically active moieties such as, but not limited to, hydroxy, amine,and carboxylic groups. As one of ordinary skill in the art understands,the particular functional groups formed will depend on the chemicalcomposition of the substrate surface and the methods and conditions usedto activate it. Often, the activation of a hydrophobic plastic surfaceusually provides a hydrophilic, electrically charged surface.

Of the various methods that can be used to activate the surface of apolymeric material, plasma treatment and corona discharge areparticularly suited for the activation of the substrate of the presentinvention. Plasmas that can be used to provide negatively charged porousplastic surfaces include, but are not limited to, plasmas of argon,oxygen, nitrogen, methanol, ethylene oxide, and acetone. Plasmas thatcan be used to provide positively charged surfaces include, but are notlimited to, ammonia and ethylenediamine. Depending on the composition ofthe substrate, its size, and the particular plasma used, the timenecessary to achieve a desired surface will vary. Typical times can varyfrom about 1 minute to about an hour. Similarly, the power necessary toachieve the desired plasma may vary from about 50 W to about 1000 W.

6.2.3. Coating

The substrate of the present invention, whether or not surfaceactivated, may be coated with various materials. When the substrate is asintered porous polymeric material, the substrate may already containsolid wetting agents, which are added during the manufacturing/sinteringprocess. Wetting agents suitable for use in the present inventioninclude, but are not limited to, surfactants and hydrophilic polymers.

Wetting agents may also be coated onto the surface of the substratethrough solution coating methods such as, but not limited to, dipping,spraying, and/or rinsing.

Specifically, the method of coating includes dipping/immersing thesubstrate into the solution. As understood by one of ordinary skill inthe art, means and durations used for the coating process depend on thespecific material and the wetting agent involved. Typically, a coating,e.g., immersing, for a duration of from about 0.5 to about 50 minutes issufficient to provide a coating. In certain cases, a coating durationfrom about 2 to about 20 or about 2 to about 10 minutes is sufficient.After the coating, the material may then be dried and/or rinsed, afterwhich it mat be coated again, if desired.

In a specific embodiment of the present invention, a sintered porouspolymeric material being used as substrate is coated with apolyelectrolyte, a surfactant, a neutral polymer, a small molecule, abiomolecule, or combinations thereof. More specially, the polymericmaterial is surface activated before being coated.

The surface activated substrate is contacted with a solution of thematerial(s) from which the first layer will be formed on the surface ofthe substrate. Specific suitable solutions are solutions of cationic oranionic polymers. The solutions can be aqueous, but organic solvents canalso be used. Specific examples are solutions of water, ethanol,isopropanol, and mixtures thereof. The contact between the activatedsubstrate and the solution is maintained for a sufficient time and at asufficient temperature for a first layer to form on the substratesurface. Specifically, layers are formed by the formation of covalentbonds and/or electrostatic interactions between functional groups on thesubstrate surface and molecules in the solution.

The interactions between functional groups on the substrate surface andmolecules in the solution can be adjusted by the type of solvent used,temperature, pH and the addition of coupling agents (e.g., DCC and EDC).For example, high pH and coupling agent concentration can promotecovalent bond formation between the substrate and the first layer ofcoating.

After the resulting coated substrate is removed from the solution, it iswashed with, for example, deionized water in an ultrasonic bath. Typicalwash times will vary depending on the solvent and the material(s) usedto form the first layer, but are often about 10 minutes or less. Thewashed, single-layer coated substrate can be optionally dried (e.g., atan elevated temperature). Elevated temperature promotes formation ofcovalent bonds.

The single-coated substrate is next contacted with a second solution.Preferably, this second solution is of molecules that are of an oppositecharge to those that form the first layer so that the second layeradheres to the first via electrostatic interactions. However, the firstlayer can also be formed from molecules that have functional groupsthat, with or without activation, can react with functional groups onthe molecules used to form the second layer. After the resultingdual-coated substrate is removed from the second solution, it ispreferably washed and dried (e.g., at an elevated temperature).

Specific examples of solutions from which the first and second layerscan be formed include, but are not limited to, polyclectrolyte solutionsof a concentration of about 10 ppm to about 100,000 ppm. As those ofordinary skill in the art will appreciate, the concentration of anyparticular solution depends on the polymer molecular weight, chargedensity and type of molecules from which a given layer is to be made.Solutions of higher molecular weight molecules generally require lowerconcentrations than those of lower molecular weight molecules.Similarly, high ionic density polymers typically require lower solutionconcentrations. Generally, biomolecules show high immobilization on asurface with opposite electric charges, particularly when the media isof low ionic strength.

Electrostatic interaction is one of the most important interactionsbetween differently charged polyelectrolytes, especially during complexformation. Different polyelectrolytes can also form covalent bondsbetween their functional groups. For example, the amino group in PEI canform amide bond with the carboxylic acid group in PAA. The formation,strength, and durability of the covalent bonds also depends on type ofsolvent, temperature, pH and coupling agents. The ratio of PEI and PAAand the coupling agent will also have an effect on the percentage ofcovalent bond formed. Coupling reagents, such asdicyclohexylcarbodiimide (DCC) and1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), can be used topromote such reactions.

Examples of different coating scenarios include electrostaticinteractions between substrate and first layer and covalent bond betweenfirst layer and second layer; covalent bond between substrate and firstlayer and covalent bond between first layer and second layer;electrostatic interactions between substrate and first layer andelectrostatic interactions between first layer and second layer; andmixed covalent bond and electrostatic interactions for both coatings.Because the molecules forming each layer can bond to the material belowit by multiple covalent and/or electrostatic interactions, typicalmaterials of the invention have highly stable coatings that areresistant to delamination and/or dissociation. Furthermore, the highstability of the present invention's multilayer coating results in lowersolubility of the coatings and, thus, provides coatings with lowleaching.

In one specific embodiment of the present invention wherein thesubstrate has been surface activated and further contains twosequentially coated layers, the first layer comprises molecules ofpolyethylenimine (PEI) and the second layer comprises molecules of apoly(acrylic acid), a copolymer containing poly(acrylic acid), or asurfactant, such as a surfactant containing fluorine. Alternatively, thefirst layer comprises molecules of polyallylammoniumchloride and thesecond layer comprises molecules of polyvinylsulfate. Specificsurfactants include, but are not limited to, cationic surfactants,anionic surfactants, amphoteric surfactants, and fluorine containingsurfactants.

The process of optionally activating a surface and contacting it with asolution of one or more compounds under conditions sufficient to form alayer on the surface can be repeated to achieve coatings of more thantwo layers. Thus, multilayer coatings of varying thicknesses, density,and uniformity can be adhered to the surfaces of a variety ofsubstrates.

For example, in one embodiment of the present invention, the substrate,such as a sintered porous polymeric material, is surface activated andfurther contains two sequentially coated layers. The material is furthercoated with one or more additional layers bound to the second or theadditional layer through covalent bonds, electrostatic interactions, orcombinations thereof. In a specific embodiment wherein a polymericmaterial having been coated with three layers, the first layer comprisesmolecules of polyethylenimine, the second layer comprises molecules of apoly(acrylic acid), and the third layer comprises of molecules ofpolyethylenimine, polyvinylamine, or a surfactant.

The manufacture of the materials of the invention often requires theformation of functional groups on the surface of a substrate. However,the utility of many materials of the invention may also depend on thenumber and types of chemical moieties on the surfaces of the finalproducts. Methods of this invention can provide substrates with avariety of chemically reactive functional groups. By way of example,functional groups that can be introduced onto the surfaces of plastic(e.g., porous plastic) substrates include amino groups (includingprimary, secondary and tertiary amines), which can be positively chargedat neutral pH. Amino-functional porous materials can be manufactured by:coating PEI or other amino group containing polyelectrolytes on porousmaterials; pre-activating materials with plasma, e-beam, or corona glow,and then solution treat porous material with amino containingpolyelectrolytes, such as PEI and other amino containing positivecharges polyelectrolytes; or solution treat porous materials thatalready be coated with negative charged polyelectrolytes, such as PAAwith amino-containing positive charge electrolytes.

Carboxylic acid groups can be introduced onto porous materials bytreating positive charged porous materials with PAA or other carboxylicacid containing polyelectrolytes solutions. Typically, positivelycharged materials have either been treated with a positively chargedpolyelectrolyte or have been activated in ammonia solution or ammoniaplasma.

Sulfonic acid functional groups can be introduced onto porous materialsby treating positive charged porous materials with PSSA or othersulfonic acid containing polyelectrolytes solutions. Typically,positively charged materials have either been treated with a positivelycharged polyelectrolyte or have been activated in ammonia solution orammonia plasma.

Poly(ethylene glycol) (PEG) molecules can be coated onto charged porousmaterials by treating charged porous materials with PEG molecules thatcontains functional groups with opposite charges. For example, a PEGmolecule having a carboxylic acid functional group can be coated onto aporous material coated with PEI.

Biomolecules can also be coated onto the substrates of this invention.For example, biotin, which is a small biomolecule that can specificallybinds to avidin and streptavidin, can be introduced onto porousmaterials by treating charged porous materials with the biotinderivatives that contain opposite charges as compared to the porousmaterials.

Many polysaccharides contain electric charges and can provide goodmatrices for cell growth and harvesting. These charged polysaccharides,such as heparin, chitosan, and CMC, can be introduced onto porousmaterials by treating oppositely charged porous materials with thepolysaccharides.

Fluoroalkyl groups, such as perfluoroalkyl groups, can be attached toporous materials by treating charged porous materials with fluoroalkylmolecules that contain opposite charges.

6.3. Characteristics and Testing of Materials

A preferred embodiment of the invention comprises a substrate and atleast two coating layers of polymers, wherein one of the polymerscontains cationic charge and another of the polymers contains anioniccharge. Such as, PEI and PAA, PEI and PSSA. Without being limited bytheory, it is believed that the adhesion of a second, oppositely chargedlayer to the first can provide a coating that is substantially morestable than the first layer alone due to the large number ofelectrostatic interactions between the two layers and the low solubilityof the material.

The present invention also encompasses materials having multilayercoatings of three or more layers adhered to the surface of a substrate(preferably a porous plastic substrate). Such multilayer complexes canbe constructed, for example, by the repeated application of compounds ofopposite electric charges. Examples of such complexes include, but arenot limited to: PEI/PAA/PEI/PAA/ . . . ,PEI/PAA/polyallylamide/polystyrenesulfonate/ . . . ,PEI/protein/PAA/protein/ . . . , and PEI/biomolecule/PAA/biomolecule/ .. . (wherein “. . . ” indicates the possible existence of additionallayers).

Depending on the use to which a particular material is put, a widevariety of small and large molecules can be used to provide coatinglayers of the invention. Various effects several classes of suchmolecules are discussed below.

6.3.1. Metal Ions

Small metallic and organic ions can be immobilized within the matrixprovided by a charged polymer-based first layer. Many metal ions cancomplex with PEI or PAA, and some ions (especially high charged ones)can be immobilized within layers of the materials of the invention:Examples of such complexes include, but are not limited to:PEI/PAA/metal ion/PEI/ . . . and PEI/anionic ions/PEI/ . . . .

Because most polyelectrolytes are excellent coordinators for heavy metalions, materials of this invention can include layers of cationic oranionic polymers in which heavy metal ions are trapped. Inorganic ionscan also be used to bridge different polyelectrolyte layers onto porousmaterials. Examples include, but are not limited to: PEI/native chargeions/PEI/Negative charge ion/PEI and PEI/PAA/Positive chargeions/PAA/positive charge ions. Table 1 shows the effect copper ions canhave on the color of porous plastic-based materials of the invention:

TABLE 1 Copper ions immobilization on porous plastics Surface Oxygenplasma PEI PEI/PAA PAA PAA/PEI Color white blue dark blue light bluedark blue

6.3.2. Dye Molecules

Small molecules that be incorporated within, or used to form one or morecoating layers include organic and inorganic dyes, particularly dyeswith electric charges. Such dyes can be used to provide materials usefulas indicators of chemical reactions, pH, and other environmentalconditions.

Most dye molecules are charged molecules and have strong interactionswith polyelectrolytes. Dye molecules can be immobilized onto porousmaterials through polyelectrolyte coating. The immobilized dye canprovide porous material with desired color and optical property. Thecolor change of immobilized dye on porous material provides applicationpossibility of using porous material as sensors.

TABLE 2 Rf values for dyes on differently treated porous plastics. Rf RfRf Surface Nile blue Poncreas Acridin orange (cationic) (anionic)(cationic) Oxygen plasma 0 0.8 0 PEI 0.65 0.1 0.5 PEI/PAA 0 0.2 0.2

6.3.3. Surfactants

Small charged organic surfactants can also be incorporated intomaterials of the invention, and can be used to provide oleophobic porousmaterials and control the wicking rates of porous materials in differentsolvents. The combination of surfactants and charged polymers can resultin stable, oleophobic surfaces that exhibit little leaching.

Small molecular surfactant with negative charges can be immobilized ontopositive polyelectrolytes coated porous plastic, such as, PEI coatedporous materials. Small molecular surfactant with positive charges canbe immobilized onto negative polyelectrolytes coated porous plastic,such as, PAA coated porous materials.

Amphoteric small molecular surfactant can be immobilized onto all kindpolyelectrolyte coated porous materials, including, negative, positiveand the complex.

TABLE 3 Wicking rates for Zonyl surfactant treated porous plastics.* PSNFS62 PSA PSK FSP Surface water ethanol water ethanol water ethanol waterethanol water ethanol Oxygen plasma 140 120 120 160 360 140 No 220 No 260 PEI 120 110 270 270 No 140  80 140 No 1020 PEI/PAA 100 110 360 320No 245 150  90 No No *Numbers are seconds/4 cm. “No” indicates nowicking occurred.

6.3.4. Biological Molecules

Biological molecules (“biomolecules”) can also be used to form one ormore coating layers on solid and porous substrates, thereby providingmaterials useful in applications such as, but not limited to, affinitybinding assays, PCR substrates, and drug delivery devices. Within themeaning of the present invention, biomolecules include, but are notlimited to, proteins, enzymes, peptides, DNA, and RNA. Preferredbiomolecules are locally charged biomolecules, which can beelectrostatically adhered to a first or subsequent layer bound to asubstrate invention. Biomolecules can be adsorbed onto the surface of acharged first or subsequent layer (i.e., to form the outermost layer ofa material of the invention), directly adhered to the substrate to forma first layer of a material, or trapped between two or more layers. Ofcourse, as with any of the other molecules that can be used to providematerials of the invention, how and where a particular biomolecule isincorporated into a material depends on the intended us of the materialand the biomolecule itself (e.g., its size, structure, and charge).

For example, biomolecules with negative charges can be directly adsorbedonto layers of positively charged surfaces, such as PEI, and can befurther stabilized with another layer of polyelectrolytes, such as PAAor PEI. Negative charged biomolecules can also be mixed with PAA in asolution used to form a first or subsequent coating layer atop asubstrate of the invention. Such mixtures can add to the chemical andphysical (e.g., susceptibility to leaching) stability of biomoleculesthat form materials of the invention. Similarly, biomolecules that havedistinct cationic and anionic ends can be incorporated into complexessuch as, but not limited to, PEI/Biomolecule/PAA.

Multiple biomolecule-based layers can also be prepared using methods ofthe invention. Examples include, but are not limited to: PEI/negativecharged biomolecule/PEI/negative charged biomolecule/ . . . andPEI/PAA/positive charged biomolecules/PAA/positive charged biomolecules.

6.4. Applications

Materials of this invention have a wide variety of applications. Forexample, specific materials of the invention exhibit stable and uniformwicking rates, and show limited leaching in pure water. Such materialscan be used in filtration and other liquid delivery devices.

The invention further encompasses oleophobic-coated materials. Forexample, porous plastics can be prepared using methods of the inventionthat have a first coating of a polyelectrolyte (e.g., PEI) and anoppositely-charged second coating made from a charge-containingfluorinated surfactant. Such materials may be used in aeration devicesand other devices that allow air, but not liquid, permeation.

The materials of the present invention can also be used to aid in thedelivery, screening, extraction, separation, or purification of variousmolecules, including biomolecules. For example, the biomolecule bindingability of porous plastic-based PEI/PAA materials are highly dependenton solution media, and can therefore be used to extract particularbiomolecules from solution. The release of biomolecules from materialsof this invention can also be controlled as to depend on surroundingsolvent conditions such as, but not limited to, pH and ionic strength.Therefore, the materials of the present invention can be used inbiomolecule purification, DNA/RNA extraction, biofluid purification,lateral flow devices, microfluidic devices, and fast screening devices.

Materials of the invention can also be used as filters in a variety ofapplications, including medical applications, where chemical leachingand contamination are unacceptable. The porous plastic-based PEI/PAAmaterials of the invention show limited leaching in aqueous solution.Chromatography is another application to which materials of theinvention can be put. For example, materials can be used to makepre-columns useful to remove impurities and contaminants in HPLCapparatuses and TLC plates. The materials can also be used asion-exchange columns. A final, non-limiting example of an application towhich materials of the invention can be put is any application thatrequires conductive porous plastics. Such plastics may be of particularuse in chemical and bio-assay technology.

7. EXAMPLES 7.1. Example 1 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EURO PLASMACD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 0.1% or 1% of PEI (BASF, MW750,000) ethanol-water solution for 10 minutes. Then the coated sheetwas rinsed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Therinsed porous plastic sheet then was immersed into certain concentrationof 0.1% or 1% PAA (Aldrich, 523925, MW 250,000) ethanol-water solutionfor 10 minutes. The coated sheet was washed with 100 times water in anultrasonic bath (VWR) at room temperature for 5 minutes. This washingwas repeated three times. The treated sheet was dried at roomtemperature.

7.2. Example 2 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with corona discharge (Corotech,Corotreator) at 200 watt for 2 minutes. The sheet become hydrophilic andhas a wicking rate of 60 seconds/4-cm. The pre-activated porous plasticsheet was immersed into 0.1% or 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into certain concentration of 0.1% or 1%PAA (Aldrich, 523925, MW 250,000) ethanol-water solution for 10 minutes.The coated sheet was washed with 100 times water in an ultrasonic bath(VWR) at room temperature for 5 minutes. This washing was repeated threetimes. The treated sheet was dried at room temperature.

7.3. Example 3 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of poly-DL-aspartic acid, sodiumsalt (Sigma, 47789-3, MW 3000) ethanol-water solution for 10 minutes.The coated sheet was washed with 100 times water in an ultrasonic bath(VWR) at room temperature for 5 minutes. This washing was repeated threetimes. The treated sheet was dried at room temperature.

7.4. Example 4 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of poly(styrenesulfonic acid-comaleic acid), sodium salt (Sigma, 43455-8, MW 20,000) ethanol-watersolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.5. Example 5 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of poly(vinylsulfate, sodiumsalt) (Sigma, 27842-4) ethanol-water solution for 10 minutes. The coatedsheet was washed with 100 times water in an ultrasonic bath (VWR) atroom temperature for 5 minutes. This washing was repeated three times.The treated sheet was dried at room temperature.

7.6. Example 6 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 0.01% of carboxymethyl cellulose,sodium salt (Sigma, 41913-1, MW 250,000) 0.01M PBS solution for 10minutes. The coated sheet was washed with 100 times water in anultrasonic bath (VWR) at room temperature for 5 minutes. This washingwas repeated three times. The treated sheet was dried at roomtemperature.

7.7. Example 7 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 0.01% of chitosan (Sigma, 44887-7) 10% acetic acid aqueous solution for 10 minutes. Then the coatedsheet was rinsed with 100 times water in an ultrasonic bath (VWR) atroom temperature for 5 minutes. This washing was repeated three times.The rinsed porous plastic sheet then was immersed into 0.01% ofcarboxymethyl cellulose, sodium salt (Sigma, 41913-1, MW 250,000) 0.01MPBS solution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.8. Example 8 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with ammonia plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PAA (Sigma, MW 250,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. The treated sheet wasdried at room temperature.

7.9. Example 9 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of poly(diallyldimethylammonia chloride) (Sigma, 40903-0, MW 500,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of poly(vinylsulfate, sodiumsalt) (Sigma, 27842-4) ethanol-water solution for 10 minutes. The coatedsheet was washed with 100 times water in an ultrasonic bath (VWR) atroom temperature for 5 minutes. This washing was repeated three times.The treated sheet was dried at room temperature.

7.10. Example 10 Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of poly(allylaminehydrochloride) (Sigma, 28322-3, MW 15,000) ethanol-water solution for 10minutes. Then the coated sheet was rinsed with 100 times water in anultrasonic bath (VWR) at room temperature for 5 minutes. This washingwas repeated three times. The rinsed porous plastic sheet then wasimmersed into 1% of poly(vinylsulfate, sodium salt) (Sigma, 27842-4)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. The treated sheet wasdried at room temperature.

7.11. Example 11 Multi-Layer Positively Charged Hydrophilic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EURO PLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 0.1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed 0.1% PAA (Sigma, MW 250,000)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. This PAA coated porousmaterial was immersed into 0.1% of PEI (BASF, MW 750,000) ethanol-watersolution for 10 minutes. Then the coated sheet was rinsed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.12. Example 12 Multi-Layer Negatively Charged Hydrophilic Surfaces

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROplasmaCD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 0.1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 0.1% PAA (Sigma, MW 250,000)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. This PAA coated porousmaterial was immersed into 0.1% of PEI (BASF, MW 750,000) ethanol-watersolution for 10 minutes. Then the coated sheet was rinsed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. This PEI coated porous plasticsheet then was immersed 0.1% PAA (Sigma, MW 250,000) ethanol-watersolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.13. Example 13 Oleophobic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of FSP (DuPont) ethanol-watersolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.14. Example 14 Oleophobic Surface

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of perfluoro-1-octanosulfonicacid, tetraethylammonium salt (Sigma, 36528-9) ethanol-water solutionfor 10 minutes. The coated sheet was washed with 100 times water in anultrasonic bath (VWR) at room temperature for 5 minutes. This washingwas repeated three times. The treated sheet was dried at roomtemperature.

7.15. Example 15 Semi-Conductive Porous Plastic

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of poly(anilinesulfonic acid)(Sigma, 52328-3, MW 10,000) ethanol-water solution for 10 minutes. Thecoated sheet was washed with 100 times water in an ultrasonic bath (VWR)at room temperature for 5 minutes. This washing was repeated threetimes. The treated sheet was dried at room temperature.

7.16. Example 16 Covalently Bound Polyelectrolyte Complex

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROplasmaCD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into certain concentration of 0.1% PAA(Sigma, MW 250,000), 0.2% Dicylohexylcarbodiimide (DCC) (Sigma, D8000-2)DMF solution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.17. Example 17 Material Coated With Anionic Dye Molecules

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 0.1% anionic dyes, such as PonceauS, sodium salt (Sigma, P3504) ethanol-water solution for 10 minutes. Thecoated sheet was washed with 100 times water in an ultrasonic bath (VWR)at room temperature for 5 minutes. This washing was repeated threetimes. The treated sheet was dried at room temperature.

7.18. Example 18 Materials Coated With Cationic Dye Molecules

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% PAA (Sigma, MW 250,000)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. The treated sheet wasdry at room temperature. Coated porous materials then was immersed into0.1% cationic dyes, such as Acridin Orange (Sigma, A 6014),ethanol-water solution. The coated sheet was washed with 100 times waterin an ultrasonic bath (VWR) at room temperature for 5 minutes. Thiswashing was repeated three times. The treated sheet was dried at roomtemperature.

7.19. Example 19 Material Coated With Poly(Ethylene Glycol) (IonicInteraction)

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% PEG-propionic (Shearwater,2M3T0P01) ethanol-water solution for 10 minutes. The coated sheet waswashed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.20. Example 20 Material Coated With Poly(Ethylene Glycol)(CovalentInteraction)

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% PEG-propionic (Shearwater,3T3T0F02), 1% Dicylohexylcarbodiimide (DCC) (Sigma, D8000-2) DMFsolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.21. Example 21 Material Coated With Anionic Surfactant

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% Sodium Dodecylsulfate (Aldrich,7 1726F) ethanol-water solution for 10 minutes. The coated sheet waswashed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.22. Example 22 Material Coated With Cationic Surfactant

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROplasmaCD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% PAA (Sigma, MW 250,000)ethanol-water solution for 10 minutes. The coated sheet was washed with100 times water in an ultrasonic bath (VWR) at room temperature for 5minutes. This washing was repeated three times. The treated sheet wasdry at room temperature. Coated porous materials then was immersed intoDodecyltrimethylammonium bromide (DTAB) (Aldrich, (26876-3),ethanol-water solution. The coated sheet was washed with 100 times waterin an ultrasonic bath (VWR) at room temperature for 5 minutes. Thiswashing was repeated three times. The treated sheet was dried at roomtemperature.

7.23. Example 23 Material Coated With Biotin

A porous plastic sheet made by Porex Corporation (pore size 7 micron,30% pore volume) was pre-activated with oxygen plasma (EUROPLASMACD600PC), at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% sulfo-NHS-LC-LC-Biotin (Pierce,21338) ethanol-water solution for 10 minutes. The coated sheet waswashed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.24. Example 24 Material Coated With Lipid

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 0.1% Fumonisin B 1 (Sigma, F 1147)or L-lysophosphatidic acid (Sigma, L7260) ethanol-water solution for 10minutes. The coated sheet was washed with 100 times water at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.25. Example 25 Material Coated With Nucleic Acids

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMACD600PC),) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 0.1% Guanosine 5′-triphosphatesodium salt (Sigma, G8877) ethanol-water solution for 10 minutes. Thecoated sheet was washed with 100 times water for 5 minutes. This washingwas repeated three times. The treated sheet was dried at roomtemperature.

7.26. Example 26 Material Coated With Protein

A porous plastic sheet made by Porex Corporation (pore size 7 micron,35% pore volume) was preactivated with oxygen plasma (EUROPLASMA, CD600PC) at 100 watt, 120 mm Hg for 5 minutes. The sheet becomehydrophilic and has a wicking rate of 60 seconds/4 cm. The pre-activatedporous plastic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of PAA sodium salt (aldrich,523925, MW 250,000) ethanol-water solution for 10 minutes. The coatedsheet was washed with 100 times water in an ultrasonic bath (VWR) atroom temperature for 5 minutes. This washing was repeated three times.The treated sheet was dried at room temperature. Treated piece wasimmersed in 0.1% Goat IgG (Sigma, I5256) at room temperature for 2hours. Then the porous material was rinsed with deionized water for 1minute three times. The final product was dried at room temperature.

7.27. Example 27 Hydrophilic Surface for Ceramic Porous Materials

A porous ceramic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of PAA (Aldrich, 523925, MW250,000) ethanol-water solution for 10 minutes. The coated sheet waswashed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.28. Example 28 Hydrophilic Surface for Metal Porous Materials

A porous metal sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of PAA (Aldrich, 523925, MW250,000) ethanol-water solution for 10 minutes. The coated sheet waswashed with 100 times water in an ultrasonic bath (VWR) at roomtemperature for 5 minutes. This washing was repeated three times. Thetreated sheet was dried at room temperature.

7.29. Example 29 Oleophobic Ceramic Materials

A porous ceramic sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of FSP (DuPont) ethanol-watersolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.30. Example 30 Oleophobic Metal Materials

A porous metal sheet was immersed into 1% of PEI (BASF, MW 750,000)ethanol-water solution for 10 minutes. Then the coated sheet was rinsedwith 100 times water in an ultrasonic bath (VWR) at room temperature for5 minutes. This washing was repeated three times. The rinsed porousplastic sheet then was immersed into 1% of FSP (DuPont) ethanol-watersolution for 10 minutes. The coated sheet was washed with 100 timeswater in an ultrasonic bath (VWR) at room temperature for 5 minutes.This washing was repeated three times. The treated sheet was dried atroom temperature.

7.31. Example 31 Wicking Characteristics

The hydrophilicity of various porous materials of the invention can beinvestigated by testing their wicking rate. For example, one end of atest piece (0.5×5 cm strip) is dipped into a 0.5 cm deep testingsolution. The time it takes for a particular solution to move up aparticular length of the strip (e.g., 4 cm) can be measured. Standardcontact angle measurements can be used to determine the hydrophobicityof materials that do not wick.

The wicking rate and stability for PEI/PAA system treated T3 materialhave been systematically tested. The results show that plasma/PEI/PAAsystem treated T3 materials have faster wicking rates for the deionizedwater than oxygen plasma treated plasma/PEI and plasma/PAA treated T3material. Most important improvement comes from the stability of thewicking rate. T3 materials with only plasma treatment return tohydrophobic during the storage at room or elevated temperature. PEI orPAA individual treatment will improve T3 material wicking stability;however, they still partially decrease the wicking rate under anelevated temperature. PEI/PAA system treated T3 material show verystable wicking rate even under an elevated temperature.

TABLE 4 Wicking rates for different aging porous materials TimeTemperature 1% PEI- 0.1% PEI- (Hrs.) (° C.) Plasma 1% PEI 0.1% PAA 1%PAA 0 60  38 36 30 40 3 60 240 60 35 35 120 60 no wicking 54 36 38 24060 no wicking 62 35 39 460 60 no wicking 60 34 39

In addition, FIG. 2 shows the wicking rates, measured in seconds/4 cm,for various polyelectrolytes complexed with PEI. The polyelectrolytesused in FIG. 2 are poly(styrene sulfonic acid-co-maleic acid)(PSSA-co-MA), poly(sodium-4-styrene sulfonate) (PS-4-SS),poly(styrene-alt-maleic acid) (PS-alt-MA), poly(vinyl alcohol-co-vinylacetate-co-itaconic acid) (PVA-co-VA-co-IA), poly(methyl vinylether-alt-maleic acid monoethyl ester) (PMVA-alt-MAME), poly(vinylsulfonic acid) (PVSA), poly(styrene-co-maleic acid) (PS-co-MA), andpoly(methyl vinyl ether-alt-maleic acid) (PMVE-alt-MA).

7.32. Example 32 Resistance to Leaching

Leaching is a common phenomenon for surface modification materials andadditives for porous materials. The leaching out of coated molecularwill reduce the life time as a filtration device and limit porousmaterials' application in highly regulated medical device area andhighly sensitive chromatography area. The leaching of differentmolecular can be quantitatively determined using a variety of analyticalmethods. Examples of the methods that can be used to determine leachinginclude the following:

-   -   (i) Polyelectrolyte: The quantitative amount leach of        polyelectrolytes and other molecules can be determined by using        UV-VIS and HPLC methods. Polyelectrolytes, such as PEI can form        complex with organic dye molecules, such as Bradford reagent.        The quantitative of this new complex can be determined using        UV-VIS spectrophotometer. The quantitative of polyelectrolytes        can be also be determined by Gel Permissive Chromatography (GPC)        or Size Exclusive Chromatography (SEC) method.    -   (ii) Biomolecules: The leach of biomolecules can be determined        using HPLC, Mass Spectrometer (MS). It is also possible to        determine biomolecule leaching using UV-VIS if the biomolecule        can catalyze certain chemical reaction. Such as horseradish        peroxidase (HRP) and catalyzed chemical reaction with        tetramethyl-benzidine (TMB).    -   (iii) Small organic molecules and surfactants: The leaching of        organic small molecules and surfactants usually can be        determined by HPLC, or UV-VIS if there is an adsorption in the        UV-VIS range.    -   (iv) Inorganic ions: UV-VIS, and ICP-MS methods can measure the        leaching amount of inorganic ions.

To achieve permanent hydrophilic porous plastics, solid form surfactantis usually applied to the porous plastics. Generally, over 50% ofapplied surfactant can be washed away from the porous plastic metrics.For example, if a porous plastic have 0.15% surfactant in it, then,0.075% of surfactant will leach out into the solution, which is the 50%of surfactant.

The amount of leaching out for PEI, PEI/PAA, and PAA/PEI complex systemcan be determined using UV-VIS by reacting with Bradford reagent. Thismethod shows the sensitivity of sub PPM in aqueous solution. Generally,the leaching amount of PEI and PEI/PAA complex depends on thepolyelectrolyte solution concentration, washing method, washing solutionpH and ionic strength

For the PEI and PEI/PAA complex treated T3 porous materials, PEI andPEI/PAA complex leaching is not sensitive to PEI or PAA concentrationsif porous materials are washed thoroughly.

TABLE 5 PEI leaching amounts in pure water PEI PEI/PAA PAA/PEISurfactant Sample (0.1–1%) (0.1–1%) (0.1–1%) (0.15%) Leaching amount 80μg/g 26 μg/g 100 μg/g 750 μg/g Leaching percentage 0.50% 0.15% 0.60% 50%

A PEI/PAA sequential treatment can significantly reduce the leaching ofPEI. No significant difference was observed among the leaching amountfor 1% PEI/1%PAA, 1%PEI/0.1%PAA, 0.1%PEI/1% PAA and 0.1% PEI/0.1% PAA.

PEI/PAA complex leaching also depends on the washing method. A thoroughwashing step after PEI application and PAA application willsignificantly reduce the leaching amount. FIG. 3 shows the leachingamounts (micro gram/gram) of two differently washed PEI/PAA treated T3materials. Sample one was three times vibration washed, Sample 2 was onetime non-vibration washed. As demonstrated, Sample 1 showed significantsmaller leaching than Sample 2.

PEI/PAA complex has different solubility in different pH and ionicstrength. Different surfaces show different leaching out under differentwashing solution. PEI coated porous plastic shows higher leaching inpure water than in PBS, PEI/PAA complex coated porous plastics showshigher leaching out in PBS and PAA only coated porous plastics showshigher leaching out in pure water. (PBS, 0.01 M, 0.15 M NaCl) (FIG. 4)

PEI/PAA treated T3 material shows much lower leaching in pure water andPBS buffer condition than surfactant treated T3. The overall leaching ofPEI is only about 1–2 percent of total immobilized PEI Vs 50% of appliedsurfactant.

It should be noted that the leaching of PEI/PAA is often undetectablewhen the amount is less than 0.1 ppm.

7.33. Example 33 Protein Biding

Protein binding was conducted by immersing differently treated porousmaterials into a protein solution, in which part of proteins have beenlabeled with enzymes or radioactive isotopes. For enzyme labeledproteins, a chemical substrate reacts with the enzyme and forms a newchemical that has a specific UV absorption band. By measuring theabsorption of newly formed chemical substance at a specific wavelength,enzyme activity and amount on the porous materials can be calculated.For the radioactive isotope labeled proteins, the amount of protein onporous material can be measured by measuring the amount of radiation.

IgG binding amount was tested using enzyme labeled goat anti-rabbit IgGon differently treated T3 porous materials. The results showed that thedifferently treated T3 material's IgG binding amount under different pH(0.01 M PBS, 0.15 M NaCl) were different. The data indicated thatuntreated T3 had a decreased IgG binding amount with increase of pH, andoxygen plasma treated T3 showed no impact of pH on its IgG binding. PEItreated T3 porous material shows the highest IgG binding at pH 7. BothPEI/PAA and PAA treated T3 porous materials showed decreased IgG bindingwith the increase of pH. PEI/PAA complex treated T3 porous materialshowed strong pH dependent IgG binding ability, which is a good propertyfor protein extraction and separation. The results are demonstrated inFIG. 5, wherein IgG binding amounts on the surface of untreated (T3),oxygen plasma treated (O₂), PEI treated. PEI-PAA treated, and PAAtreated T3 material under different pH values (i.e., 6, 7 and 8) areshown.

FIG. 6 shows the differently treated T3 porous material's IgG bindingability (pH 7) under different ionic strength (deionized water, 0.01 MPBS buffer, 0.1 M PBS buffer, which translate into 0, 0.15, and 1.5ionic strength, respectively). The data indicate that untreated T3porous material and oxygen plasma treated T3 porous material do not haveionic strength dependent IgG binding. PEI treated T3 porous material hadthe highest IgG binding at ionic strength of 0. 15. Both PEI/PAA and PAAtreated T3 materials showed significant decrease of IgG binding fromionic strength 0 to ionic strength of 0.15. However, there was littledifference between ionic strength of 0.15 and 1.5. PEI/PAA complextreated T3 porous material showed ionic strength dependent IgG bindingability, which is a good property for protein extraction and separation.

FIG. 7 shows the results of protein (IgG) binding to differently treatedmaterials. The materials have an average pore size of 10 micro metersand the binding assays were conducted at a pH value of 7.18.

FIG. 8 shows the results of protein (IgG) binding to materials treatedwith different polyelectrolytes. The materials have an average pore sizeof 7 micro meters and the binding assays were conducted under a pH valueof 7.

As those skilled in the art will readily recognize, this invention isnot limited to the details provided above or shown in the attachedfigures. Instead, the invention is best understood with reference to thefollowing claims.

1. A multi-layer coated material comprising a substrate, a first layer,a second layer, and a third layer wherein: the substrate comprises asurface-activated porous polymeric material having an average pore sizeranging from 1 μm to 200 μm; the first layer consists of polyelectrolytemolecules bound to a surface of the substrate through covalent bonds,electrostatic interactions, or combinations thereof; the second layerconsists of polyelectrolyte molecules bound to the first layer throughcovalent bonds, electrostatic interactions, or combinations thereof; andthe third layer consists of molecules of a surfactant directly bound tothe second layer through covalent bonds, electrostatic interactions, orcombinations thereof; wherein the polyelectrolyte molecules in the firstlayer and the second layer are different and are independently selectedfrom the group consisting of polyethylenimine, quaternizedpolyacrylamide, polyvinylamine, polyallylamine, chitosan, poly(acrylatetrialkyl ammonia salt ester), cellulose, poly(acrylic acid),polymethylacrylic acid, polyvinylsulfate, poly(styrenesulfonic acid),poly(vinylsulfonic acid), poly(toluene sulfonic acid), heparin, alginicacid, dextran sulfate, adipic acid, poly(methyl vinyl ether-alt maleicacid), surfactant, polyallylammonium chloride, and salts thereof andcopolymers thereof.
 2. The material of claim 1, wherein the porouspolymeric material is a polyolefin, polyester, polyurethane,polycarbonate, polyetheretherketone, poly(phenylene oxide), poly(ethersulfone) or nylon.
 3. The material of claim 2, wherein the polyolefin isethylene vinyl acetate, ethylene methyl acrylate, polyethylene,polypropylene, ethylene-propylene rubber, ethylene-propylene-dienerubbers, poly(1-butene), polystyrene, poly(2-butene), poly(1-pentene),poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), 1,2poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene,polychloroprene, poly(vinyl acetate), poly(vinylidene chloride),poly(vinylidene fluoride), poly(tetrafluoroethylene) or a mixturethereof.
 4. The material of claim 1, wherein the polyelectrolytemolecules of the first layer are selected from the group consisting ofpolyethylenimine, quaternized polyacrylamide, polyvinylamine,polyallylamine, chitosan, poly(acrylate trialkyl ammonia salt ester),cellulose, polyacrylic acid, polymethylacrylic acid,poly(styrenesulfonic acid), poly(vinylsulfonic acid), poly(toluenesulfonic acid), poly(methyl vinyl ether-alt-maleic acid), surfactant,dextran sulfate, hyaluronic acid, heparin, alginic acid, adipic acid,and salts thereof and copolymers thereof.
 5. The material of claim 1,wherein the polyelectrolyte molecules of the second layer are selectedfrom the group consisting of poly(acrylic acid), polymethylacrylic acid,polyvinyl sulfate, poly(styrenesulfonic acid), poly(vinylsulfonic acid),poly(toluene sulfonic acid), poly(methyl vinyl ether-alt-maleic acid,and salts thereof and copolymers thereof.
 6. The material of claim 1,wherein the first layer consists of molecules of polyethylenimine andthe polyelectrolyte molecules of the second layer are selected from thegroup consisting of poly(acrylic acid) and copolymers thereof.
 7. Thematerial of claim 1, wherein the first layer consists of molecules ofpolyallylammoniumchloride, and the second layer consists of molecules ofpolyvinylsulfate.
 8. The material of claim 1, wherein the substrate isfurther coated with one or more additional layers, wherein eachadditional layer is bound to the layer below it through covalent bonds,electrostatic interactions or combinations thereof.
 9. The material ofclaim 8, wherein the one or more additional layers comprisespolyelectrolyte molecules selected from the group consisting ofpolyethylenimine, quaternized polyacrylamide, polyvinylamine,polyallylamine, chitosan, poly(acrylate trialkyl ammonia salt ester),cellulose. poly(acrylic acid), polymethylacrylic acid, polyvinylsulfate,poly(styrenesulfonic acid), poly(vinylsulfonic acid), poly(toluenesulfonic acid), heparin, alginic acid, dextran sulfate, adipic acid,poly(methyl vinyl ether-alt maleic acid), surfactant, polyallylammoniumchloride and salts thereof and copolymers thereof.
 10. The multi-layercoated material of claim 1, wherein the material is hydrophilic.
 11. Themulti-layer coated material of claim 10 which has a wicking rate ofabout 7.5 sec./cm to about 37.5 sec./cm.
 12. A multi-layer coatedhydrophilic material comprising a substrate, a first layer, a secondlayer, and a third layer, wherein the substrate comprises a surfaceactivated porous polymeric material having an average pore size rangingfrom 1 μm to 200 μm, the first layer consists of polyethyleniminemolecules bound to a surface of the substrate through covalent bonds,electrostatic interactions, or combinations thereof, the second layerconsists of polyelectrolyte molecules selected from the group consistingof poly(acrylic acid) and copolymers thereof bound to the first layerthrough covalent bonds, electrostatic interactions, or combinationsthereof, and the third layer consists of molecules of surfactantdirectly bound to the second layer through covalent bonds, electrostaticinteractions, or combinations thereof.
 13. A multi-layer coated materialcomprising a substrate, a first layer, a second layer, and a third layerwherein: the substrate comprises surface-activated porous polyethylenehaving an average pore size ranging from 1 μm to 200 μm; the first layerconsists of molecules of polyethylenimine bound to a surface of thesubstrate through covalent bonds, electrostatic interactions, orcombinations thereof; the second layer consists of molecules selectedfrom the group consisting of quaternized polyacrylamide, polyvinylamine,polyallylamine, chitosan, poly(acrylate trialkyl ammonia salt ester),cellulose, poly(acrylic acid), polymethylacrylic acid, polyvinylsulfate,poly(styrenesulfonic acid), poly(vinylsulfonic acid), poly(toluenesulfonic acid), poly(methyl vinyl ether-alt-maleic acid), surfactant,dextran sulfate, hyaluronic acid, heparin, alginic acid, adipic acid,and salts thereof and copolymers thereof, bound to the first layerthrough covalent bonds, electrostatic interactions or combinationsthereof; and the third layer consists of molecules of a surfactantdirectly bound to the second layer throuah covalent bonds, electrostaticinteractions, or combinations thereof.
 14. The multi-layer coatedmaterial of claim 13, wherein the molecules of the second layer areselected from the group consisting of poly(acrylic acid) and copolymersthereof.
 15. A multi-layer coated material comprising a substrate, afirst layer, a second layer, and a third layer wherein: the substratecomprises a surface-activated porous polymeric material having anaverage pore size ranging from 1 μm to 200 μm; the first layer consistsof polyelectrolyte molecules bound to a surface of the substrate throughcovalent bonds, electrostatic interactions, or combinations thereof; thesecond layer consists of polyelectrolyte molecules bound to the firstlayer through covalent bonds, electrostatic interactions, orcombinations thereof; wherein the polyelectrolyte molecules in the firstlayer and the second layer are different and are independently selectedfrom the group consisting of a phosphate, polyethylenimine,poly(vinylimidazoline), quaternized polyacrylamide, polyvinylpyridine,poly(vinylpyrrolidone), polyvinylamine, polyallylamine, chitosan,poly(acrylate trialkyl ammonia salt ester), cellulose, poly(acrylicacid), polymethylacrylic acid, poly(styrenesulfonic acid),poly(vinylsulfonic acid), poly(toluene sulfonic acid), poly(methyl vinylether-alt-maleic acid), surfactant, dextran sulfate, hyaluronic acid,heparin, alginic acid, adipic acid, chemical dye, and salts thereof andcopolymers thereof; and the third layer consists of molecules of asurfactant directly bound to the second layer throuah covalent bonds,electrostatic interactions, or combinations thereof.
 16. The multi-layercoated material of claim 15, wherein the substrate comprisespolyethylene, the first layer consists of polyethylenimine and themolecules of the second layer are selected from the group consisting ofpoly(acrylic acid) and copolymers thereof.
 17. The multi-layer coatedmaterial of claim 15, wherein the surfactant is an amphotericsurfactant.
 18. The multi-layer coated material of claim 17, wherein theamphoteric surfactant comprises a fluorinated surfactant.